The Research Of Broadband Amplifier-similariton Fiber Laser

Because of its in high speed optical communication,optical imaging,sensing and medical applications,high-energy ultrashort pulse light sources have attracted much attentions.Mode-locked technology is one of effective method to generate ultrashort optical pulse.Since the soliton energy quantization effect,the energy of traditional soliton optical pulse is limited to about 0.1 nJ.Compared with the traditional soliton,the similariton fiber laser can produce higher energy pulses.Because the self-similar evolution is located in gain fiber of laser,this similariton pulse is called amplifier-similariton pulse.On the one hand,amplifier-similariton pulse can tolerate large nonlinear phase shift without wave-breaking,.thus,it can produce more pulse energy;on the other hand,it can be transformed the accumulated of nonlinear phases shift into linear frequency chirp,thus compressed pulse can achieve nearly transform limit pulse,broadband amplifier-similariton optical pulse can produce more narrow pulse width.In this paper,by using numerical simulation method,we research the optimized design of broadband amplifier similariton fiber laser,concrete research content is as follows:1.Starting from the formation mechanism of passively mode-locked pulse,we introduced the progress of mode-locked fiber laser,and respectively expound the formation mechanism of traditional soliton and similariton.2.Starting from Maxwell's equations,the light pulse transmission equation,generalized nonlinear Schrodinger equation,was deduced.Then we introduced the correction equation with gain:Ginsburg-Landau equation,and we outlined the basic method of numerical solving the above equation,the slit-step Fourier numerical method.Finally we introduced the theory model of amplifier similariton fiber laser and the assessment criteria of similaritons,the misfit parameter M.3.Using numerical simulation method,we researched the forming process of amplifier-similariton pulse in an all-normal dispersion of ytterbium doped fiber laser.Furthermore,we researched the influence of the length of single-mode fiber,the pump power,the spectral filter bandwidth,the length of photonic crystal fiber and the output coupling ratio on the pulse output.By optimizing the parameters,we obtained an optimal value with the pulse energy of 23.8 nJ,spectral bandwidth of 186.6 nm,to chirp pulse width of 22.5 fs,pulse peak power of 1.26 MW.4.Using numerical simulation method,we researched the forming process of amplifier-similariton pulse in an net-normal dispersion of erbium doped fiber laser.Furthermore,we researched the influence of the length of single-mode fiber,the pump power,the length of erbium doped fiber,the spectral filter bandwidth,the length of photonic crystal fiber and the output coupling ratio on the pulse output.By optimizing the parameters,we obtained an optimal value with the pulse energy of 15.2 nJ,spectral bandwidth is 182.7 nm,to chirp pulse width of 37.5 fs,pulse peak power of 0.4 MW.